Formulation of an Optimal Mix of Indigenous Clay in Water Well Drilling

In two neighbouring communities in the Niger delta region, water-well drillers routinely substitute indigenous clays in different proportions into drilling-mud, used during water-wells drilling activities. This article examined the effect of different clay formulations and the resultant mud weights using Scheffe’s simplex lattice. Drilling-muds were designed from clay from Koko, Ubeji and the imported bentonite. The clay samples from the two localities were prepared into three types of water-based drilling-mud, namely; E, F and G. Each type had 11 sub-types with different proportions of indigenous clays and bentonite. The results revealed no impediment to the use of local clay in drilling shallow depths. In all combinations of indigenous clays and bentonite, the resultant mud weights ranged from a specific gravity of 8.55 (100% Koko clay) to 8.60 (100% Ubeji clay) and 8.90 (pure bentonite). All formulations were observed to exert sufficient pressure against the formation/ terrain. The practice of substitution of local indigenous mud for imported mud (bentonite) was found to be reliable. The substitution of imported drilling material with local material is expected to be cost -efficient with huge reduction in drilling cost